Engine starter gearing



United States Patent ENGINE STARTER GEARING Donald L. Hager, Elmira, N. Y., assignor to Bendix Aviation Corporation, a corporation of Delaware Application June 28, 1954, Serial No. 439,498 4 Claims. c1. 74'-7 The present invention relates to engine starter gearing and more particularly to that type which engages automatically upon actuation of the starting motor, and maintains such engagement until a satisfactory start has been secured.

It is an object of the present invention to provide a novel starter drive of the above type which is small and compact as compared to more conventional types of drive having similar load capacities, and which includes a coupling that slips when a predetermined maximum load is exceeded, thereby protecting the parts from being overloaded.

It is another object to provide such a device in which the overload slip coupling also serves as an overrunning clutch which permits the pinion to rotate with the engine gear without driving the starting motor when the engine starts.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation partly broken away and in section of a preferred embodiment of the invention showing the parts in normal or idle position;

Fig. 2 is a similar view showing the parts in cranking position; and

Fig. 3 is a similar view showing the parts in the positions assumed when the engine starts and causes the drive to overrun the starting motor.

In Fig. 1 of the drawing there is illustrated a power shaft 1 which may be the extended armature shaft of a starting motor not illustrated. A hollow sleeve 2 is rigidly mounted on the power shaft as by means of a cross pin 3 and retaining wire 4, and is provided for a portion of its length with splines 5 on which a driving coupling member 6 is slidably but non-rotatably mounted. A stop ring 7, seated in a circumferential groove in the sleeve 2 forms an abutment for the coupling member 6, and a plurality of spring washers 8 located between the coupling member and a flange 9 on the sleeve 2 yieldably urges the coupling member against said stop rmg.

A screw shaft 11 is slidably journaled on the smooth portion of the sleeve 2 and is provided with inclined teeth 12 which cooperate with similar teeth 13 on the coupling member 6, initial engagement of the teeth being maintained by a spring washer 14 located between the end of the screw shaft 11 and an abutment ring 15 fixed on the end of the sleeve 2 by means of a lock ring 16.

A pinion 17 is slidably journaled on the power shaft 1 for movement into and out of mesh with an engine ring gear 18, and means for actuating the pinion from the screw shaft 11 is provided comprising a control nut 19 which is threaded on said screw shaft and is retained in one end of a barrel member 21 by means of a lock ring 22. Control nut 19 is provided with radial lugs 23 slidably mounted in slots 24 in the barrel member to form a splined connection therewith. The op- 2,127,394 Patented Dec. 20, 1955 posite end of the barrel member is rigidly connected with the pinion as indicated at 25.

A mesh-enforcing spring 26 is located between the control nut 19 and an internal shoulder 27 in the barrel for normally holding the control nut against the lock ring 22.

A detent member 28 is slidably mounted for radial movement in the control nut 19 and is pressed against the surface of the screw shaft 11 by means of a spring 29. The screw shaft is formed with a recess 31 adapted to receive the detent 28 when the parts move toward cranking position, the recess terminating in a shoulder 32 which restricts demeshing movement of the pinion until the detent is withdrawn by centrifugal force. The screw shaft is also provided with an inclined shoulder 33 positioned to cooperate with the detent to prevent drifting of the pinion and its associated parts away from idle position.

In operation, starting with the parts in the positions illustrated in Fig. 1, initial rotation of the power shaft 1 by the starting motor is transmitted through the coupling member 6 to the screw shaft 11 and thereby causes the control nut 19 to be traversed on the screw shaft to bring the pinion 17 into mesh with the engine gear 18 as shown in Fig. 2. When the meshing movement of the control nut 19 is arrested by the abutment ring 15, the screw shaft is forced backward by the screwjack action of the control nut thereon, thereby moving the coupling member 6 back against the pressure of the spring members 8, correspondingly forcing together the teeth 12, 13 of the screw shaft and coupling member until this movement of the screw shaft is arrested by the stop ring 7.

If the initial starting torque, which is a combination of the electrical torque of the motor and the torque derived from the deceleration of the rotating parts as the cranking load is assumed, exceeds a predetermined maximum, the inclined teeth 13 of the coupling member slip over the teeth 12 as permitted by further compression of the springs 8 until excess torque has been dissipated. Thereafter, cranking of the engine takes place without further slippage until a successful start is secured.

When the engine fires, the acceleration of the pinion 17 causes it to thread itself back on the screw shaft 11 until detent 28 engages shoulder 32. The pinion is thus held in partial mesh with the engine gear 18 while the pinion, barrel, and screw shaft assembly overrun in unison, as permitted by the release of pressure on the clutch teeth 12, 13. In case of a false start, cranking will consequently be resumed as soon as the engine slows down to the speed of the starting motor.

When the engine has become reliably self-operative, acceleration of the pinion and control nut above a predetermined speed causes the detent 28 to be withdrawn, permitting the control nut to thread itself back on the screw shaft and thereby return the parts to their idle positions.

Although but one form of the invention has been shown and described in detail it will be understood that changes may be made in the precise form and arrangement of the parts without departing from the spirit of the invention.

I claim:

1. In an engine starter drive a power shaft, a sleeve fixed thereon, a screw shaft slidably journalled on the sleeve, a pinion slidably and rotatably mounted on the power shaft for movement into and out of mesh with a gear of the engine to be started, a control nut on the screw shaft, a barrel member connecting the control nut and pinion, an abutment on the sleeve limiting the travel of the screw shaft and of the nut in the direction to mesh the pinion with the engine gear, a driving coupling member non-rotatably mounted on the sleeve, said coupling member and screw shaft having interengaging position or the coupling member'and inclined torque-transmitting teeth, and means for yield- 3. An engine starter drive as set forth in claim 2 in which said stop means also serves to define the normal 2,727,894 7 g I v maintain said spring under initial compression. v

4. An engine starter drive as set forth in claim 3 including further a comparatively light spring means interposed between the screw shaft and said abutment urging the screw shaft into engagement with the coupling member, but permitting the screw shaft to overrun the coupling member when the engine starts.

I References Cited in the file of this patent UNITED STATES PATENTS 2,546,948 Miller Mar. 27, 1951 FOREIGN PATENTS 809,406 France Dec. 3, 1936 

